1. Field of the Invention
The present invention relates to an assembly method of a carriage assembly in which magnetic head assemblies are assembled in a carriage with a plurality of arms of a magnetic disk drive.
2. Description of the Related Art
In a magnetic disk drive using a magnetic disk, a magnetic head is moved over a recording surface of the magnetic disk and data is recorded on tracks provided on the recording surface.
A magnetic head assembly including a magnetic head is supported on a rotatable carriage. The carriage is rotated by means of a voice coil motor so that the magnetic heads are moved relative to the magnetic disk.
Recently, in order to increase a memory capacity, a magnetic disk drive is provided with a plurality of, for example, two or three magnetic disks. The magnetic disks are rotated and magnetic head assemblies are moved in a swinging manner over recording surfaces provided on top and bottom surfaces of each magnetic disk. Thereby, data is recorded on the recording surfaces.
In this type of magnetic disk drive having a plurality of magnetic disks, a plurality of arms are provided on the carriage. A plurality of magnetic head assemblies are attached to the arms such that each magnetic disk is sandwiched by the magnetic head assemblies on both sides.
According to one assembling method, there are provided a carriage having a plurality of arms each having a through-hole, and a plurality of magnetic head assemblies having cylindrically projecting mount portions designed to be fitted in the through-holes. The mount portions are fitted in the through-holes from both ends of the through-holes and fixed by calking. Thus, each arm is provided with a pair of head assemblies.
According to another assembling method of the so-called "interlock" type, there are provided magnetic head assemblies having cylindrically projecting first mount portions designed to be fitted in through-holes of the arms, and magnetic head assemblies having cylindrically projecting second mount portions designed to be fitted in the first mount portions. The first mount portions are fitted in the through-holes from first ends of the through-holes, respectively, and the second mount portions are inserted in the through-holes from second ends of the through-holes, respectively. The inserted end portions of the second mount portions are fitted in the end portions of the first mount portions and are fixed by calking. According to this interlock-type method, the thickness of each arm can be reduced by a degree corresponding to overlapping between the first and second mount portions.
In the assembly, high precision is required. Specifically, small-sized magnetic head assemblies are conventionally attached to small-sized arms arranged with small intervals by manual work, and not by mechanical work.
In the former assembly method, the mount portions of the magnetic head assemblies are manually inserted in the through-holes of the arms from both sides of the through-holes so that all the magnetic head assemblies are situated in predetermined positions, i.e. each pair of magnetic head assemblies are situated to face each other inwardly between adjacent two of the arms.
At this time, since the mount portions of the magnetic head assemblies are simply inserted in the through-holes of the arms, the magnetic head assemblies are unstable and tend to be displaced.
Thereafter, a calking steel ball is passed through the inner holes of the mount portions under pressure, thereby fixing the mount portions to the arms by calking. The steel ball has a diameter slightly greater than the inside diameter of each mount portion. Thus, with the passing of the steel ball under pressure, each mount portion is deformed so as to bite into the inner surface of the associated through-hole and fixed to the associated arm. Thereby, the magnetic head assemblies are assembled and situated to sandwich the magnetic disks from both sides.
On the other hand, according to the latter assembly method, the first mount portions are manually inserted in the through-holes of the arms successively from the first ends of the through-holes, and the second mount portions are inserted in the through-holes from the second ends of the through-holes and fitted in the first mount portions. As a result, each pair of magnetic head assemblies are situated to face each other between adjacent two of the arms.
At this time, since the mount portions of the magnetic head assemblies are simply inserted in the through-holes of the arms, the magnetic head assemblies are unstable and tend to be displaced.
Thereafter, a calking steel ball is passed through the inner holes of the second mount portions under pressure, thereby fixing the first and second mount portions to the arms by calking.
In each of the above assembly methods, a great deal of time is needed to attach the magnetic head assemblies to the arms. Specifically, in the case where the magnetic head assemblies are set, while a first group of magnetic head assemblies are unstably set on the arms, a second other group of magnetic head assemblies need to be set on the arms.
This process must be carried out carefully since the second set of magnetic head assemblies must be set without moving the already set first group of magnetic head assemblies, by making use of narrow spaces between the arms.
In particular, in the interlock-type assembly method, a first group of magnetic head assemblies are unstably disposed on first surfaces of the arms, and the first and second mount portions are engaged in the through-holes. These steps tend to displace the already set magnetic head assemblies (by external force), and require careful handling.
The work with low efficiency is thus continued from the fixation of the first magnetic head assembly to the fixation of the last magnetic head assembly. The work load on the operator is considerably great, and a great deal of working time is needed. Consequently, the magnetic head assemblies cannot be attached to the carriage efficiently.